Method for production of paving blocks

ABSTRACT

The fracture-free paving block (1) comprises a cement block substrate (1-1) and a top solid layer (1-2), and is characterized in that the top layer is selected from a cured cement mortar layer and a tile-like layer firmly bonded to the substrate with cement mortar; the top layer is bonded to the block substrate with lateral margins (2) of 1 to 8 mm wide in horizontal distance (1 5 ) from the peripheral edges of the substrate: and the vertical distance (1 6 ) from the surface of the top layer to the peripheral edge of the substrate is 5 to 50 mm. The method for producing the paving block (1) having a tile-like top layer comprises applying adhesive cement mortar between the back of the top layer (1-2) and the upper surface of the substrate (1-1); placing the top layer on the substrate with the above-mentioned margins (2) of the substrate surface: and applying vibration and/or pressurization between the top layer and the substrate.

DESCRIPTION

1. Technical Field

This invention relates to a novel paving block to be installed on thegrounds such as streets and floors, and to a method for production ofthe paving blocks.

2. Background Art

The plane configurations of conventional paving blocks have a variety ofshapes such as rectangles, squares, triangles, other polygons, circles,ovals, and other shapes. The peripheral side lines of the block can bestraight, a curved line, a wave-like line or a combination thereof, asfar as the blocks can be joined at an interval of a few millimeters whenthey are installed. The same plane configurations as those conventionalblocks are employed in the present paving blocks.

A perspective view of a conventional paving block of rectangularparallelepiped is illustrated in FIG. 9, wherein a ceramic tile isbonded onto a cement concrete block having the same plane dimensions asthe tile. Such conventional tile-bonded blocks have been produced by (1)placing a tile upside-down on the bottom of a casting mold and thencasting concrete mortar thereon, or (2) casting concrete mortar into themold and placing a tile thereon (e.g. Japanese Laid-open Pat.Application No. 61-142202). According to the above-mentioned method (1),some dissolved components of concrete mortar flow down and deposit onthe tile surface to form efflorescence. According to the method (2),lots of voids remain or are formed at the interface between the tile andblock, which largely deteriorate the bonding strength between them.Moreover, durability is also decreased because water such as rain oftenpermeates into the bonded interface through the voids.

Incidentally, a tile-bonded panel is known for walls composed of amultiplicity of tiles bonded onto a substrate board. In such tilepanels, large bonding strength of tile is not especially needed becausea large external force is not pressed on such wall panels, and alsopermeation of water is prevented because joint intervals of the tiles onthe substrate board are filled with jointing paste. Thus, suchtile-bonded panels for walls should be clearly distinguished fromtile-bonded paving blocks.

The paving blocks are installed on the grounds such as streets at aninterval of about 2 to 5 mm. The joint intervals of blocks thusinstalled are filled with sand (not with jointing paste).

The paving blocks installed on the grounds such as streets receive avariety of heavy loads from cars or the like. As a result, the blocksmove to each other by complicated forces applied thereto and are ofteninclined together, whereby the shoulder portions of adjacent blockscollide with each other and break off.

SUMMARY OF THE INVENTION

The main object of the present invention is to solve the above-mentionedbreaking or fracture problems and to provide novel paving blocks whereinthe fracture of the shoulder portions is substantially eliminated.

There is thus provided, according to the present invention, a pavingblock having a structure comprising a block substrate consistingessentially of inorganic hydraulic cement and aggregate, and a top solidlayer bonded to the upper surface of the block substrate: characterizedin that the top layer is selected from a cured cement mortar layerfirmly bonded to the substrate by its self-adhesive property and atile-like layer firmly bonded to the substrate with cured cement mortar;the top layer is bonded to the block substrate with lateral margins ofthe substrate around the top layer of about 1 to 8 mm wide in horizontaldistance from the peripheral edges of the substrate; and the verticaldistance from the surface of the top layer to the peripheral edge of thesubstrate is about 5 to 50 mm.

It is preferred that the top solid layer mentioned above be firmlybonded to the block substrate with squeeze-out deposits of cured cementmortar around the top layer, whereby the bonding layer of cement mortaris substantially free of voids to increase bonding strength and toprevent the bonded interface from permeation of water.

There is also provided, according to the present invention, a method forproducing a paving block comprising a block substrate and a tile-liketop layer bonded to the upper surface of the block substrate, withlateral margins of about 1 to 8 mm wide in horizontal distance from theperipheral edges of the substrate and with vertical distance of about5˜50 mm from the surface of the top layer to the peripheral edge of thesubstrate; which method comprises

applying adhesive cement mortar between the back of the top layer andthe upper surface of the substrate,

placing the top layer on the substrate with the above-mentioned marginsof the substrate surface, and

applying vibration and/or pressurization between the top layer and thesubstrate to firmly bond them and form squeeze-out deposits of theadhesive cement mortar around the top layer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing a paving block of the presentinvention;

FIGS. 2A and 2B are cross-sectional views of the paving block of FIG. 1;

FIG. 3 is a perspective view showing a paving block of the presentinvention;

FIGS. 4A through 4D is a schematic partial side views showingconfigurations of the block;

FIGS. 5 and 6 are cross-sectional views showing embodiments of theblocks;

FIG. 7 is a cross-sectional view showing an embodiment of a substrate ofthe blocks;

FIGS. 8A through 8E are cross-sectional views showing steps forproducing the block; and

FIG. 9 is a perspective view of a conventional block.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Configurations,Dimensions, etc. of the Blocks

FIG. 1 shows a perspective view of a paving block 1 composed of a blocksubstrate 1--1 and a cement mortar top layer 1-2 according to thepresent invention. FIG. 2A shows a cross-sectional view of adjacentlyarranged two blocks of FIG. 1. FIG. 2B is a schematic cross-sectionalview of the blocks of FIG. 2A which are inclined together when heavyweight is loaded from cars or the like. FIG. 3 shows a perspective viewof the present paving block composed of a block substrate 1--1 and atile-like top layer 1-2 bonded to the substrate with adhesive cementmortar, wherein squeeze-out deposits 6 of the cement mortar is observedaround the top layer.

In FIGS. 1 and 2A, the configurations and dimensions of the block 1 areshown, wherein l, is a lateral length, l₂ is a side length and l₃ is aheight of the block substrate. In general, the length of l₁ or l₂ isabout 8 to about 50 cm. The height l₃ is at least about 3 cm and in therange of about 3-20 cm, generally at least about 4 cm and in the rangeof about 4˜20 cm, preferably about 4˜15 cm, and normally about 4˜10 cm.The numeral 2 shows lateral margins on the surface of the blocksubstrate 1--1, the width or horizontal distance l₅ from the peripheraledges being about 1˜8 mm and normally about 1˜5 mm. The lateral margin 2can be substantially horizontal or can be inclined in a sloping or roundfashion as shown in FIG. 4. The numeral 3 shows a vertical side of thetop layer 1-2 and the 4 shows a preferred embodiment of bevelingportions or round corners of the top layer, the horizontal distance l₄of the beveling or round corners being substantially zero to a fewmillimeters. The numeral 5 shows a surface of the top layer 1-2, thevertical distance l₆ from the surface 5 of the top layer to theperipheral edge of the margin 2 of the substrate 1--1 being about 5˜50mm and normally about 5˜30 mm. Incidentally as shown in FIG. 2A, thepaving blocks are installed on the ground at an interval of about 2˜5mm, and thus the distance l between the adjacent top layers of theinstalled blocks is about 4 mm or more. The intervals and distances lare filled with sand, when the blocks are installed.

FIGS. 4A through 4D are partial side views of the paving blocks 1showing the examples of configurations of the round corners (orbeveling) 4 and margins 2 of the blocks. These configurations are alsoas effective as those shown in FIGS. 1 and 3.

FIG. 5 is a cross-sectional view of a paving block according to thepresent invention, showing a tile-like, solid top layer 1-2 is placedand bonded onto a dish-like depression 9 of a block substrate 1--1 withan adhesive cement mortar layer 7 between the top layer and thedepression. The upper surface of the block substrate comprisesperipheral margins 2, depression 9, and slopes 10 which connect thedepression to the margins. The angle θ of the slope is generally about30˜60 degrees and typically about 45 degrees to the horizontaldirection. Such slopes are useful to receive the top layer in the properposition of the depression. The slopes, however, are not essential, andthe depression can be connected to the margins with vertical walls. Thedepression 9 has such a configuration as to receive the back of thetile-like top layer and the adhesive cement mortar. FIG. 6 shows across-sectional view of another paving block, wherein the depression 9of the block substrate 1--1 has some spaces 11 at the slopes 10 forholding squeeze-out deposits 6 of the adhesive cement mortar. The depthof the depression 9 is generally in the range of about 1.5˜10 mm andnormally about 2˜5 mm. Incidentally, the depression 9 can have somecut-outs at the corners or walls of the depression to readily drive outsome excess adhesive cement mortar and to prevent the corners or wallsfrom fracture.

FIG. 7 shows a cross-sectional view of a block substrate 1--1 similar tothose shown in FIGS. 5 and 6, wherein the lower major portion of thesubstrate comprises cement concrete 12 containing comparatively coarseaggregate and the upper surface of the substrate is substantiallycovered with cured cement mortar 8 containing comparatively fineaggregate, whereby the shoulders including the margins 2 of thesubstrate is provided with good appearances and the tile-like top layercan be readily bonded to the substrate without interruption of thecoarse aggregate. The cured cement mortar layer has a thickness of about2˜10 mm and normally about 3˜4 mm. In FIG. 7, the cured mortar layer 8provides the depression 9 and margins 2 of the block substrate. Suchcured cement mortar layers, however, can also be employed in other blocksubstrates as shown in FIGS. 1 and 3. (2) Materials for Producing theBlocks

The term cement means an inorganic hydraulic material and represented byportland cement, alumina cement, fly ash cement, blast furnace cement,slag cement, and mixtures thereof. In general, portland cement is used.Conventional aggregate used for cement is also employed in the presentinvention, such as sand, slag and gravel. The cement material such asmortar and concrete can be colored as necessary.

As to general sizes of aggregate, cement concrete for the blocksubstrate may contain comparatively coarse aggregate, the sizes of whichare those of remaining on 5 mm-square screen and normally those ofremaining on 5 mm-square screen and passing through 20 mm-square screen.The sizes of aggregate for a cement mortar top layer 1-2 or a curedcement mortar 8 covering cement concrete substrate are those passingthrough 5 mm-square screen and preferably through 4 mm-square screen.The sizes of fine aggregate for the adhesive cement mortar 7 are thosepassing through 1.2 mm-square screen and preferably through 1 mm-squarescreen.

Incidentally, cement mortar containing such fine aggregate can be usedas adhesive cement mortar. It is preferred that the adhesive cementmortar comprises a major amount of the cement mortar and a minor amount(e.g. about 40˜5% by weight) of an organic adhesive polymer such asstyrene butadiene rubber (SBR) latex or acrylic polymer emulsion.

The tile-like top layers 1-2 include, for example, ceramic tile producedfrom minerals, and similar sintered plates produced from inorganicsubstances; natural stone plates of granite, marble, slate, etc.; andartificial stone plates such as decorative cement boards andresin-modified cement boards. The tile-like layers, however, are notrestricted to those shown above, as far as they have good bondingproperties, sufficient strength and good appearances. (3) Steps forBonding the Top Layer onto the Block Substrate

When the block comprises a cured mortar top layer and a block substrate,the block can be successfully produced by casting concrete mortar forthe substrate into a mold and then casting cement mortar thereon,followed by applying thereto an upper mold for the top layer and adensification step such as vibration.

FIGS. 8A through 8E are cross-sectional views showing preferredembodiments or steps for bonding a tile-like top 1-2 layer onto a blocksubstrate 1--1. FIG. 8A shows a mortar applicator moving sideways (cf.arrow) on a masking board 23 and over the masked tile-like top layer1-2. The applicator 21 is equipped with a slant wall 22 angled at about30˜60 degrees shown by θ to the horizontal direction and arranged in thecross-machine direction, whereby adhesive cement mortar 7 is uniformlyapplied through the opening 23 of the masking board 24 by the movingslant wall onto the back of the top layer (cf. FIG. 8B). The adhesivemortar is applied in the thickness of about 2˜5 mm. The applicator 21can also be used to apply the mortar onto the upper surface of the blocksubstrate 1-2 with or without the depression 9.

The mortar-backed top layer (cf. FIG. 8B) is turned upside down and isplaced on the upper surface of the substrate 1--1 (cf. FIG. 8C).Vibration (e.g. 1000 to 10,000 cycles/minute) and/or pressurization(e.g. 0.1 to 0.5 Kgf/square cm) and preferably the both actions areapplied onto the top layer by means of a clamping plate 25 placed on thetop layer, whereby the adhesive cement mortar is squeezed out and oftenflowed out onto the side surfaces of the substrate (cf. FIG. 8D). Theexcess mortar 7 remaining on the side surfaces is effectively scrapedaway by means of a frame 26 having a horizontally sectional shape of theblock substrate 1--1 (cf. FIG. 8E). Incidentally, the frame 26 can becomposed of a metal frame having inside edges of a resilient material.

(4) Experiments for Demonstrating Non-fracture or Fracture of PavingBlocks

The following paving blocks were produced for the experiments.

(A) Conventional block without peripheral margins

(Dimensions: 98 mm×198 mm×80 mm in height)

(B) Conventional block without margins and with beveling

(about 45 degrees, 2 mm in horizontal distance) at top edges thereof

(Dimentions: 98 mm×198 mm×80 mm in height)

(C) Block having top layer with margins of 2 mm wide

(top layer: 8 mm high from the margins)

(block substrate: 98 mm×198 mm×80 mm in height)

(D) Block having top layer with beveling and margins of 2 mm wide

(top layer; 8 mm high from the margin, with beveling about 45 degrees, 2mm in horizontal distance)

(block substrate; 98 mm×198 mm×80 mm in height)

Hundred (100) pieces each of the paving blocks (A), (B), (C) and (D)were installed on the ground in 10 lines and 10 rows, respectively. Amortar truck having gross weight of 7 metric tons was driven 600 timeson the paving blocks thus installed. As a result, the blocks (D)according to the present invention showed no substantial fracture. Theblocks (C) according to the present invention showed light fracture in 2pieces out of 100 pieces of the blocks; such small fracture wasevaluated to be practically satisfactory. The conventional blocks (A)showed serious fracture in 38 pieces out of 100 pieces. The conventionalblocks (B) also showed serious fracture in 13 pieces out of 100 piecesof the blocks.

It has not been fully clarified why the present paving blocks having theperipheral margins 1˜8 mm wide (preferably 1˜5 mm) and the top layer5˜50 mm in height (preferably 5˜30 mm) are substantially prevented fromsuch serious fracture. The main reasons therefor, however, areconsidered due to the following actions:

(a) The present paving block is provided with the margins and top layer.Also, the block substrate is substantially covered with a rather thicktop layer. Thus, the edges of the top layer are substantially preventedor moderated from collision, and the shoulders of the substrate aresubstantially protected with the covering top layer from fracture evenwhen the shoulders of the adjacent substrates collide with each other.

(b) Because the top layer is bonded with the margins onto the blocksubstrate, heavy weight on the top layer is loaded on the inner sides ofthe surfaces of the block substrate. Thus, the force of collision of thesubstrate shoulders is somewhat moderated.

Incidentally, when the width of margins is more than about 8 mm or theheight of the top layer is less than about 5 mm, the protection of thesubstrate shoulders as mentioned above (a) will be less expected. Whenthe height of the top layer is more than about 50 mm, uniform dispersionof the loads pressed on the top layer into the whole block body isworsened thus deteriorating the durability of blocks.

INDUSTRIAL APPLICABILITY

Fracture of paving blocks installed on the grounds are substantiallyeliminated according to the present paving blocks and method forproduction thereof. Thus, the blocks according to the present inventionare especially useful for block pavement where heavy weight is loaded.Such paving blocks can be effectively produced according to the methodof the present invention.

We claim:
 1. A method for producing a paving block comprising a blocksubstrate and a solid top layer selected from the group consisting of atile layer and a cured cement mortar layer bonded to the upper surfaceof the block substrate having a thickness in the range of 3 cm to 20 cm,with lateral margins of 1 to 8 mm wide in horizontal distance from theperipheral edges of the substrate to the top layer and with verticaldistance of 5 to 50 mm from the surface of the top layer to theperipheral edge of the substrate, said method comprising:applyingadhesive cement mortar between the back of the top layer and the uppersurface of the substrate, placing the top layer on the substrate withthe above-mentioned margins of the substrate surface, and applyingvibration and/or pressurization between the top layer and the substrateto firmly bond them and form squeeze-out deposits of the adhesive cementmortar around the top layer.
 2. The method according to claim 1, inwhich the adhesive cement mortar is applied onto the back of the toplayer and the mortar-backed top layer is placed on the substrate.
 3. Themethod according to claim 1, in which adhesive cement mortar flowed outonto the side surfaces of the substrate in the course of the vibrationand/or pressurization step is scraped away by means of a frame having ahorizontally sectional shape of the block substrate.
 4. The methodaccording to claim 1, in which the adhesive cement mortar comprises amajor amount of cement mortar and a minor amount of an organic adhesivepolymer.
 5. The method according to claim 1, in which the adhesivecement mortar is uniformly applied through the opening of a maskingboard by moving sidewards a mortar applicator having a slant wall on themasking board.
 6. The method according to claim 1, in which the blocksubstrate comprises cement concrete containing coarse aggregate, and theupper surface of the block substrate is substantially covered with curedcement mortar containing fine aggregate.
 7. The method according toclaim 6, in which the coarse aggregate is of a size which remains on a 5mm-square screen and the fine aggregate is of a size which passesthrough a 5 mm-square screen.
 8. The method according to claim 6, inwhich the upper surface of the block substrate has a depression forreceiving the back of the solid top layer and the adhesive cement mortarand the solid layer is bonded into the depression.
 9. The methodaccording to claim 7, in which the depression is connected with slopesto the peripheries of the block substrate.
 10. The method according toclaim 1, in which the upper surface of the block substrate has adepression for receiving the back of the solid top layer and theadhesive cement mortar and the solid layer is bonded into thedepression.
 11. The method according to claim 10, in which thedepression is connected with slopes to the peripheries of the blocksubstrate.
 12. A method for producing a paving block comprising aconcrete block substrate and a cured cement mortar top layer containingfine aggregate bonded to the upper surface of the block substrate havingthickness in the range of 3 cm to 20 cm, with lateral margins of 1 to 8mm wide in horizontal distance from the peripheral edges of thesubstrate to the top layer and with vertical distance of 5 to 50 mm fromthe surface of the top layer to the peripheral edge of the substrate,said method comprising:casting concrete mortar for the substrate into amold; casting cement mortar for the top layer onto the cast concretemortar; applying an upper mold for the top layer onto the cast cementmortar and concrete mortar; and then subjecting the cast materials inthe mold to a densification step.
 13. The method according to claim 12,in which the lateral margins are 1 to 5 in width, and the verticaldistance between the top layer surface and the peripheral edge is 5 to30 mm.
 14. The method according to claim 12, in which the cement mortartop layer is firmly bonded to the concrete block substrate withsqueeze-out deposits of the cement mortar around the top layer, saidsqueeze-out deposits being formed by said densification whereby a bondedinterface between the top layer and the block substrate is substantiallyfree of voids to increase bonding strength and to prevent the bondedinterface from permeation of water.
 15. A method according to claim 12wherein said densification step comprises vibration.
 16. The methodaccording to claim 12, in which the fine aggregate is of a size whichpasses through a 5 mm-square screen.